Abstract: A method of synchronizing accesses to shared data in a multiprocessing system having an atomic swap capability. A distinguished lock value is defined. A processor which wishes to access a shared data memory location performs an atomic swap of the lock value to the shared data memory location. If the data received from the atomic swap is equivalent to the lock value the processor knows that the memory location has been locked by another processor. The processor then repeats the atomic swap at intervals until data is received which is not equivalent to the lock value. The processor operates on the data and then performs a write to the shared data memory location to replace the lock value with the updated data. In an alternate embodiment, in situations where a unique lock value cannot be defined, an array is created to store lock values associated with particular shared data memory locations.

Abstract: Three new, efficient protocols for providing communications between a user's application program, a Multiprocessing Library, and the host Operating System is described. These new protocols are termed WAKEUP, GIVEUP, and CONTEXT-TO-USER-SPACE. They utilize the concept of a conduit through which the Operating System and the user application program can communicate without the need for expensive system calls. A primary use for the new protocols is the scheduling of multiple Central Processing Units (CPUs) into a single user program in a multi-CPU, multiprogramming, multi-tasking environment. WAKEUP allows a master process to quickly request the asynchronous scheduling of slave processes to help execute parallel tasks. GIVEUP allows a slave process time to finish a task before Operating System interruption. Once completed with its task, there is no need to save the context of the slave process.